U.S. patent application number 14/925671 was filed with the patent office on 2016-05-05 for power tool counterweight arrangement and mass member.
The applicant listed for this patent is Black & Decker Inc.. Invention is credited to Thomas F. Doehner, Philip T. Miller, Daniel H. Sides, JR., Qiang J. Zhang.
Application Number | 20160121450 14/925671 |
Document ID | / |
Family ID | 54366150 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160121450 |
Kind Code |
A1 |
Miller; Philip T. ; et
al. |
May 5, 2016 |
POWER TOOL COUNTERWEIGHT ARRANGEMENT AND MASS MEMBER
Abstract
A power tool may include a motor and a drive shaft having a
first end coupled to the motor and a second end eccentrically
coupled to a platen by a retainer bearing and eccentric sleeve. A
counterweight component may be coupled to the second end of the
drive shaft to counteract imbalance generated by rotation of the
retainer bearing, eccentric sleeve and platen. The counterweight
component may include a counterweight coupled to the second end of
the drive shaft, between the eccentric sleeve and the platen.
Alignment of the counterweight may be offset with respect to a
centerline of the drive shaft to counteract vibration generated due
to interaction of the platen with a workpiece. The counterweight
component may also include a counterweight mass member coupled to a
sector of the counterweight to counteract vibration generated due
to interaction of the platen with a workpiece.
Inventors: |
Miller; Philip T.; (Phoenix,
MD) ; Sides, JR.; Daniel H.; (New Freedom, MD)
; Zhang; Qiang J.; (Lutherville, MD) ; Doehner;
Thomas F.; (York, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Black & Decker Inc. |
Newark |
DE |
US |
|
|
Family ID: |
54366150 |
Appl. No.: |
14/925671 |
Filed: |
October 28, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62074936 |
Nov 4, 2014 |
|
|
|
Current U.S.
Class: |
451/357 |
Current CPC
Class: |
B24B 23/03 20130101;
B23Q 11/0035 20130101; B24B 41/007 20130101 |
International
Class: |
B24B 23/03 20060101
B24B023/03; B23Q 11/00 20060101 B23Q011/00 |
Claims
1. A power tool, comprising: a housing; a motor in the housing; a
drive shaft, a first end portion of the drive shaft being coupled
to the motor; a platen; a retainer bearing coupled to a first
surface of the platen; an eccentric sleeve coupled to a second end
portion of the drive shaft, the eccentric sleeve being coupled in
the retainer bearing to eccentrically couple the drive shaft to the
platen; an eccentric mass, including the eccentric sleeve, the
retainer bearing and the platen coupled to the second end portion
of the drive shaft; and a counterweight coupled to the second end
portion of the drive shaft, between the first surface of the platen
and the eccentric sleeve, wherein the counterweight is positioned
such that a counterweight axis defined along a radial centerline of
the counterweight is offset by a predetermined angle with respect
to an orbit radius axis of the eccentric mass.
2. The power tool of claim 1, wherein the orbit radius axis is
defined by a line extending laterally through a longitudinally
extending centerline of the drive shaft and a longitudinally
extending centerline of the eccentric mass.
3. The power tool of claim 1, wherein the predetermined angle is
greater than 0.0 degrees and less than or equal to 9.0 degrees.
4. The power tool of claim 3, wherein the predetermined angle is
greater than 0.0 degrees and less than or equal to 6.0 degrees.
5. The power tool of claim 1, wherein the predetermined angle is
determined based on an orbit radius defined by a lateral distance
between a longitudinally extending centerline of the drive shaft
and a longitudinally extending centerline of the eccentric
mass.
6. The power tool of claim 5, wherein a second surface of the
platen, opposite the first surface of the platen, faces an exterior
of the tool, the second surface of the platen being configured to
receive an abrasive sheet engaging a finishing surface of a
workpiece during operation of the power tool.
7. The power tool of claim 6, wherein the counterweight is
configured to counteract forces generated due to interaction
between the abrasive sheet and the finishing surface based on the
position of the counterweight, the position of the counterweight
being offset by the predetermined angle with respect to the orbit
radius axis, and the counterweight being positioned adjacent to the
first surface of the platen and proximate the second surface of the
platen and the abrasive sheet coupled thereto.
8. A power tool, comprising: a motor; a drive shaft, a first end
portion of the drive shaft being coupled to the motor; a platen; a
retainer bearing coupled to a first surface of the platen; an
eccentric sleeve coupled to a second end portion of the drive
shaft, the eccentric sleeve being coupled in the retainer bearing
to eccentrically couple the drive shaft to the platen; a
counterweight coupled to the second end portion of the drive shaft,
between the first surface of the platen and the eccentric sleeve;
and a mass member included on the counterweight, positioned on a
peripheral diametric edge portion of the counterweight.
9. The power tool of claim 8, wherein the mass member is positioned
on one side of an orbit radius axis of an eccentric mass of the
tool, the eccentric mass including the eccentric sleeve, the
retainer bearing and the platen coupled to the second end portion
of the drive shaft.
10. The power tool of claim 9, wherein the orbit radius axis is
defined by a line extending laterally through a longitudinally
extending centerline of the drive shaft and a longitudinally
extending centerline of the eccentric mass.
11. The power tool of claim 8, wherein the mass member is
integrally formed with the counterweight as a single unit.
12. The power tool of claim 8, wherein a second surface of the
platen, opposite the first surface of the platen, faces an exterior
of the tool, the second surface of the platen being configured to
receive an abrasive sheet engaging a finishing surface of a
workpiece during operation of the power tool.
13. The power tool of claim 12, wherein the counterweight and mass
member coupled thereto are configured to counteract forces
generated due to interaction between the abrasive sheet and the
finishing surface based on the position of the mass member on the
counterweight, and the position of the counterweight adjacent to
the first surface of the platen and proximate the second surface of
the platen and the abrasive sheet coupled thereto.
14. The power tool of claim 12, further comprising a housing,
wherein the motor, the drive shaft, the retainer bearing, the
eccentric sleeve and the counterweight are received in the housing,
with the first surface of the platen facing an interior of the
housing.
15. A power tool, comprising: a motor; a drive shaft, a first end
portion of the drive shaft being coupled to the motor; a platen; a
retainer bearing coupled to the platen; a fan coupled to the drive
shaft, the fan including a first counterweight and a hub portion,
the drive shaft extending through an opening in the hub portion; a
sleeve coupled to the hub portion of the fan, the sleeve being
coupled in the retainer bearing; and a second counterweight coupled
to a second end portion of the drive shaft, between the first
surface of the platen and the sleeve.
16. The power tool of claim 15, wherein the opening in the hub
portion is eccentrically positioned in the hub portion.
17. The power tool of claim 16, wherein a mass of a first sector of
the hub portion is greater than a mass of a second sector of the
hub portion, such that the first sector defines the first
counterweight.
18. The power tool of claim 17, wherein the first counterweight and
the second counterweight are configured to counteract forces
generated due to interaction between an abrasive sheet coupled to a
second surface of the platen and a finishing surface of a workpiece
based on a position of the first counterweight and a position of
the second counterweight adjacent to the first surface of the
platen and proximate the second surface of the platen and the
abrasive sheet coupled thereto.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 62/074,936, filed Nov. 4, 2014, titled "Power
Tool Counterweight Arrangement And Mass Member," which is
incorporated herein by reference in its entirety.
FIELD
[0002] This document relates, generally, to a power tool, and in
particular, to a power tool for sanding a workpiece.
BACKGROUND
[0003] Power tools, and in particular, power tools used to provide
a desired surface finish on a workpiece, may include, for example,
polishers, sheet sanders, random orbit sanders, and the like. Some
of these types of power tools may employ an eccentric motion to
remove material from the surface of the workpiece, and improve
surface finish.
SUMMARY
[0004] In one aspect, a power tool may include a housing, a motor
in the housing, a drive shaft, a first end portion of the drive
shaft being coupled to the motor, a platen, a retainer bearing
coupled to a first surface of the platen, an eccentric sleeve
coupled to a second end portion of the drive shaft, the eccentric
sleeve being coupled in the retainer bearing to eccentrically
couple the drive shaft to the platen, and a counterweight coupled
to the second end portion of the drive shaft, between the first
surface of the platen and the eccentric sleeve. The counterweight
may be positioned such that a counterweight axis defined along a
radial centerline of the counterweight is offset by a predetermined
angle with respect to an orbit radius axis of an eccentric mass
including eccentric sleeve, retainer bearing and platen coupled to
the second end portion of the drive shaft.
[0005] In another aspect, a power tool may include a motor, a drive
shaft, a first end portion of the drive shaft being coupled to the
motor, a platen, a retainer bearing coupled to a first surface of
the platen, an eccentric sleeve coupled to a second end portion of
the drive shaft, the eccentric sleeve being coupled in the retainer
bearing to eccentrically couple the drive shaft to the platen, a
counterweight coupled to the second end portion of the drive shaft,
between the first surface of the platen and the eccentric sleeve,
and a mass member included on the counterweight, positioned on a
peripheral diametric edge portion of the counterweight.
[0006] In another aspect, a power tool may include a motor, a drive
shaft, a first end portion of the drive shaft being coupled to the
motor, a platen, a retainer bearing coupled to the platen, a fan
coupled to the drive shaft, the fan including a first counterweight
and a hub portion, the drive shaft extending through an opening in
the hub portion, a sleeve coupled to the hub portion of the fan,
the sleeve being coupled in the retainer bearing, and a second
counterweight coupled to a second end portion of the drive shaft,
between the first surface of the platen and the sleeve.
[0007] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other features
will be apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1A is a perspective view of an example implementation
of an eccentric motion power tool, and FIG. 1B is an exploded view
of the tool shown in FIG. 1A.
[0009] FIGS. 2A and 2B are bottom views of a sanding tool, and FIG.
2C is a cross-sectional view of the sanding tool shown in FIGS. 2A
and 2, in accordance with embodiments as broadly described
herein.
[0010] FIG. 2D is a graph of vibration levels of sanding tools
having counterweights positioned at varying offset angles, and with
varying orbit radii, in accordance with embodiments as broadly
described herein.
[0011] FIG. 3A is a bottom view of a sanding tool, and FIG. 3B is a
cross-sectional view of the sanding tool shown in FIG. 3A, in
accordance with embodiments as broadly described herein.
[0012] FIG. 4 is a cross-sectional view of a sanding tool, in
accordance with embodiments as broadly described herein.
DETAILED DESCRIPTION
[0013] An example implementation of an eccentric motion power tool
is shown in FIGS. 1A-1B. The exploded view of the example sanding
tool 10 shown in FIG. 1B illustrates a housing 11 in which a motor
is received, the motor rotating a drive shaft 12. A sanding platen
16, or sanding pad 16, may include a substantially planar outer
surface 16A to which an abrasive finishing sheet, such as, for
example, sandpaper may be affixed. A bearing retainer 14 may be
positioned on an inner surface of the platen 16, at a location that
is eccentric to the drive shaft 12, with an eccentric sleeve 15
coupling the drive shaft 12 to the retainer bearing 14, to convert
the rotational force of the motor transmitted by the drive shaft 12
into an orbital movement of the platen 16.
[0014] To counteract imbalance in the eccentric coupler 15/retainer
bearing 14/platen 16 generated due to the eccentric coupling of the
platen 16 to the drive shaft 12 during operation, in some
embodiments, the tool 10 may include a counterweight 18 coupled to
the drive shaft 12. A coupling device 19, such as, for example, a
washer 19A and a fastener 19B, may couple the counterweight 18 in
position at the end of the drive shaft 12, with a dust cap 17
covering the assembled counterweight 18 and drive shaft 12. In some
embodiments, the counterweight 18 may be positioned opposite the
center of gravity of the platen 16, for example, approximately 180
degrees from the center of gravity of the platen 16. Positioning of
the counterweight 18 in this manner may counteract imbalance and
reduce vibration when the motor is rotating the drive shaft 12.
However, when the platen 16, and in particular, a sheet of
sandpaper attached to the outer surface 16A of the platen 16,
contacts a workpiece during operation, vibration of the tool 10 may
increase due to additional external forces introduced by resistance
between the finishing surface of the workpiece and the
sandpaper.
[0015] To counteract an additional force, or force vector,
generated due to the resistance between the finishing surface of
the workpiece and the sandpaper, in some embodiments, the
counterweight may be arranged at a relatively small offset angle
with respect to an orbit radius axis. In some embodiments, the
counterweight may be positioned as close to the source of this
additional vibration and/or imbalance as possible, for example, as
close to the lower surface of the platen as possible, for example,
between the bearing retainer and the lower surface of the platen.
Arranging the counterweight at a relatively small offset angle with
respect to the orbit axis radius, and/or arranging the
counterweight as close to the lower surface of the platen as
possible may balance the rotating masses to reduce vibration and
counteract the force vector generated due to the interaction
between the sandpaper and the workpiece, thus reducing effective
vibration of the tool engaged with a workpiece during
operation.
[0016] FIGS. 2A and 2B are bottom views of a sanding tool 200, in
accordance with an example implementation as broadly described
herein, with a platen and a dust cap of the sanding tool 200
removed so that an arrangement of internal components is visible,
and FIG. 2C is a cross-sectional view of the sanding tool 200 shown
in FIGS. 2A and 2B.
[0017] As shown in FIGS. 2A and 2B, the tool 200 may include a
housing 210 in which a drive shaft 220 driven by a motor 230 is
housed. The drive shaft 220 may be rotated by the motor 230 about a
driven shaft centerline 220A. An eccentric sleeve 250 may be
eccentrically positioned around a distal end portion of the drive
shaft 220, centered about an eccentric mass centerline 250A that is
offset from the driven shaft centerline 220A. The eccentric sleeve
250 may be retained by a bearing retainer 240 surrounding the
eccentric sleeve 250, with the bearing retainer 240 coupled to an
inner surface portion of a platen 260, or sanding pad 260. The
platen 260 may include an outer surface 260A to which an abrasive
sheet 265, such as sandpaper, may be affixed. A counterweight 280
may be coupled to the distal end of the drive shaft 220, between
the bearing retainer 240/eccentric sleeve 250 and the platen 260. A
coupling device 290, including, for example, a fastener 291
extending through a washer 292 positioned in a recess of the
counterweight 280 and into the distal end portion of the drive
shaft 220, may couple the counterweight 280 in position relative to
the bearing retainer 240, eccentric sleeve 250 and drive shaft 220,
with a dust cap 270 positioned between the end of the assembled
components and the platen 260.
[0018] As shown in FIGS. 2B and 2C, an orbit radius R may be
defined by a distance between the driven shaft centerline 220A and
the eccentric mass centerline 250A, with an orbit radius axis RA
defined by a line extending laterally through the longitudinally
extending driven shaft centerline 220A and the longitudinally
extending eccentric mass centerline 250A. A counterweight axis CA
may be defined by a line radially bisecting the counterweight 280,
with an angle .theta. formed between the orbit radius axis RA and
the counterweight axis CA. The angle 0.theta. may define an offset
angle of the counterweight 280 with respect to the orbit radius
axis RA. Offset of the counterweight 280, for example by the offset
angle .theta., and proximity of the counterweight 280 to the outer
surface 260A of the platen 260, may counteract imbalance, and may
reduce vibration of the tool 200 engaged with a workpiece during
operation.
[0019] In some embodiments, the offset angle .theta. may be greater
than 0.0 and less than or equal to approximately 9.0 degrees to
achieve a desired reduction in vibration levels. In some
embodiments, the offset angle .theta. may be greater than 0.0
degrees and less than or equal to 6.0 degrees to achieve a desired
reduction in vibration levels. In some embodiments, the offset
angle .theta. may be between approximately 6.0 degrees and 9.0
degrees to achieve a desired reduction in vibration levels. In some
embodiments, arrangement of the counterweight so that a portion of
the counterweight mass is located as close to the plane of the
workpiece as possible, and at an relatively small offset angle with
respect to the orbit radius, as described above, may reduce
vibration by up to approximately 40%, depending on, for example,
orbit radius, operation speed and the like. For example, in one
implementation, a tool vibration level, when the tool is actively
engaged with a workpiece during operation, may be less than
approximately 2.5 m/s.sup.2. Various combinations of orbit radius
R, offset angle .theta. and resulting reductions in vibration
levels are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Orbit Radius R Angle .theta. Vibration
(m/s.sup.2) Combination (mm) (Degrees) Unit 1 Unit 2 Unit 3 1 1.3 0
4.1 4.4 2 1.3 3 3.0 3.1 2.8 3 1.3 6 2.9 2.6 3.1 4 1.3 9 3.8 4.2 4.6
5 1.3 12 6.0 -- -- 6 1.4 0 3.8 -- -- 7 1.4 3 2.9 3.1 3.1 8 1.4 6
2.5 1.8 2.7 9 1.4 9 2.4 2.7 3.0 10 1.4 12 2.9 3.1 -- 11 1.4 15 --
4.4 -- 12 1.2 3 3.1 3.4 3.4 13 1.2 6 3.1 3.0 3.1 14 1.2 9 4.7 5.3
4.2
[0020] As shown in Table 1 above, and in the graph of FIG. 2D,
example implementations of sanding tools, units 1, 2 and 3, may
achieve varying reductions in vibration level when the
counterweight is positioned at a relatively small offset angle
.theta.. The graph shown in FIG. 2D illustrates vibration levels
for three different units 1, 2 and 3, taken at three different
orbit radii (1.2 mm, 1.3 mm and 1.4 mm), ranging from an offset
angle .theta. of approximately 0.0 degrees to an offset angle
.theta. of approximately 12.0 degrees.
[0021] For example, in a first example implementation of a sanding
tool represented by combination 3 in Table 1, an example orbit
radius of 1.3 mm and an offset angle of approximately 6.0 degrees
may result in a vibration level of approximately 2.6 m/s.sup.2,
resulting in an approximately 30% reduction in vibration compared
to the same tool having an orbit radius of 1.3 mm, but with the
counterweight aligned with the driven shaft centerline (i.e., an
offset angle of 0.0 degrees). In a second example implementation,
represented by combination 8 in Table 1, an example orbit radius of
1.4 mm and an offset angle of approximately 6.0 degrees may result
in a vibration level of approximately 2.5 m/s.sup.2, resulting in
an approximately 34% reduction in vibration compared to the same
tool having an orbit radius of 1.4 mm, but with the counterweight
aligned with the driven shaft centerline (i.e., an offset angle of
0.0 degrees). In a third example implementation, represented by
combination 9 in Table 1, an example orbit radius of 1.4 mm and an
offset angle of approximately 9.0 degrees may result in a vibration
level of approximately 2.4 m/s.sup.2, resulting in an approximately
37% reduction in vibration compared to the same tool having an
orbit radius of 1.4 mm, but with the counterweight aligned with the
driven shaft centerline (i.e., an offset angle of 0.0 degrees).
[0022] As noted above, arrangement of the counterweight so that at
least a portion of the counterweight mass is located as close to
the plane of the workpiece as possible, and at an relatively small
offset angle with respect to the orbit radius, rather than aligned
with the driven shaft centerline, as described above, may reduce
vibration to varying degrees, depending on various factors
associated with a particular tool implementation, such as, for
example, orbit radius, operation speed and the like.
[0023] FIG. 3A is a bottom view of a sanding tool 300, in
accordance with an example implementation as broadly described
herein, with a platen and a dust cap of the sanding tool 300
removed so that an arrangement of internal components is visible,
and FIG. 3B is a cross-sectional view of the sanding tool 300 shown
in FIG. 3A.
[0024] The tool 300 may include a housing 310 housing a drive shaft
320 driven by a motor 330 to rotate about a driven shaft centerline
320A, with an eccentric sleeve 350 eccentrically positioned around
a distal end portion of the drive shaft 320, centered about an
eccentric mass centerline 350A, and retained by a bearing retainer
340 that is coupled to an inner surface portion of a platen 360,
similar to the tool 200 described above with respect to FIGS.
2A-2C. The platen 360 may include an outer surface 360A to which an
abrasive sheet 365, such as sandpaper, may be affixed. A
counterweight 380 may be coupled to the distal end of the drive
shaft 320, between the bearing retainer 340/eccentric sleeve 350
and the platen 360, by a coupling device 390, including, for
example, a fastener 391 and a washer 392, with a dust cap 370
positioned between the end of the assembled components and the
platen 360.
[0025] The counterweight 380 may include a counterforce mass member
385. The counterforce mass member 385 may be coupled to, or affixed
to, or integral to the counterweight 380, and may be positioned to
a particular sector of the counterweight 380, such as, for example,
along a diameter line 381 of the counterweight 380. The
counterforce mass member 385 may be made of the same material as
the counterweight 380, or may be made of a different material than
the counterweight 380. In the example implementation shown in FIGS.
3A and 3B, the counterforce mass member 385 is substantially
cylindrical. However, a shape or contour, relative size, and/or
positioning of the counterforce mass member may be different that
the example shown in FIGS. 3A and 3B.
[0026] The counterforce mass member 385 may be positioned on the
counterweight 380, on one side of the orbit radius axis RA opposite
the remainder of the counterweight 380, to increase the weight on
the one side of the counterweight 380. The additional mass added to
the one side of the counterweight 380 by the counterforce mass
member 385 may counteract imbalance and vibration generated by the
rotating masses, that is, the rotation of the structure including
the eccentric sleeve 350, bearing retainer 340 and platen 360, thus
reducing vibration of the tool 300 engaged with a workpiece during
operation.
[0027] As discussed above, in the example implementation shown in
FIGS. 2A-2C, the counterweight 280 is offset by the offset angle
.theta. to counteract imbalance and vibration generated by the
rotating masses (for example, rotation of the structure including
the eccentric sleeve 250, bearing retainer 240 and platen 260). In
the example implementation shown in FIGS. 3A and 3B, the
counterforce mass member 385 provided on the counterweight may
counteract the imbalance and vibration generated by the rotating
masses, without this type of angular offset of the counterweight
380.
[0028] The counterweight 380 and the counterforce mass member 385
may work together to counteract the imbalance and vibration
generated by the rotating masses, and may reduce vibration of the
tool 300 engaged with a workpiece during operation. In some
embodiments, arrangement of the counterweight 380 and the
counterforce mass member 385 so that a portion of the counterforce
mass is located as close to the plane of the workpiece as possible,
with the counterweight 380 and the counterforce mass member 385
positioned to counteract imbalance due to vibration generated by
the rotating masses, may reduce vibration by up to approximately
40%, as discussed in detail above, so that when the tool 300 is
actively engaged with a workpiece during operation, vibration may
be less than approximately 2.5 m/s.sup.2.
[0029] FIG. 4 is a cross-sectional view of a sanding tool 400, in
accordance with an example implementation as broadly described
herein.
[0030] The tool 400 may include a housing 410 housing a drive shaft
420 driven by a motor 430 to rotate about a driven shaft centerline
420A. A sleeve 450 may be retained by a bearing retainer 440 that
is coupled to an inner surface portion of a platen 460, similar to
the tool 200 described above with respect to FIGS. 2A-2C and the
tool 300 described above with respect to FIGS. 3A-3B. The platen
460 may include an outer surface 460A to which an abrasive sheet
465, such as sandpaper, may be affixed.
[0031] A first counterweight 480, in the form of a weighted fan
480, may be positioned on the drive shaft 420, adjacent to the
bearing retainer 440, to generate a flow of air within the housing
410 for cooling of the components received in the housing 410
and/or to direct finishing material/sanding dust removed from the
workpiece into a collection receptacle. A distal end portion of the
drive shaft 420 may be received in an opening 481 formed in a hub
portion 482 of the fan 480. In some embodiments, the opening 481
may be eccentrically positioned in the hub 482, so that a first
sector of the hub 482 includes more material than a second
(opposite) sector of the hub 482, thus weighting the fan 480 in the
area of the first (weighted) sector. In some embodiments, the
distal end portion of the drive shaft 420 may be tapered in a
portion of the drive shaft 420 corresponding to the weighted sector
of the hub 482 of the fan 480. The hub portion 482 of the weighted
fan 480 may be coupled in the sleeve 450 and the bearing retainer
440, which is in turn coupled to the platen 460. In some
embodiments, a second counterweight 486 may be coupled to the
distal end of the drive shaft 420, between the bearing retainer
440/sleeve 450/hub portion 482 of the weighted fan 480 and the
platen 460.
[0032] The first counterweight 480 and the second counterweight 486
may work together to counteract the imbalance and vibration
generated by the rotating masses, and may reduce vibration of the
tool 400 engaged with a workpiece during operation. In some
embodiments, arrangement of the first counterweight 480 and the
second counterweight 486 so that a portion of the counterweight
mass is located as close to the plane of the workpiece as possible,
with the first counterweight 480 and the second counterweight 486
positioned to counteract imbalance due to vibration generated by
the rotating masses, may reduce vibration by up to approximately
40%, as discussed in detail above, so that when the tool 400 is
actively engaged with a workpiece during operation, vibration may
be less than approximately 2.5 m/s.sup.2.
[0033] While certain features of the described implementations have
been illustrated as described herein, many modifications,
substitutions, changes and equivalents will now occur to those
skilled in the art. It is, therefore, to be understood that the
appended claims are intended to cover all such modifications and
changes as fall within the scope of the implementations. It should
be understood that they have been presented by way of example only,
not limitation, and various changes in form and details may be
made. Any portion of the apparatus and/or methods described herein
may be combined in any combination, except mutually exclusive
combinations. The implementations described herein can include
various combinations and/or sub-combinations of the functions,
components and/or features of the different implementations
described.
* * * * *